UK region

Water hardness in London

Average 286 ppm across 330 postcode districts — classified as hard.

  • Range 150–350 ppm
  • Counties 1
  • Suppliers Affinity Water, SES Water, Severn Trent Water, South East Water, Thames Water, Yorkshire Water
Regional average
286
ppm CaCO₃
Hard
Soft
Moderate
Hard
Very hard
0100200300400+
286
Avg ppm
150
Min ppm
350
Max ppm
330
Postcodes

Water Hardness Across London

The average water hardness in the London region is 286 ppm, classified as hard. Across 330 postcode districts, hardness ranges from 150 ppm to 350 ppm.

The region is served by Affinity Water, SES Water, Severn Trent Water, South East Water, Thames Water, Yorkshire Water. Water hardness varies by county — see the breakdown below or check your specific postcode.

Looking for London Water Hardness?

For detailed postcode-level data on London's water hardness (306 ppm avg, very hard), see our dedicated London page with all 330 postcode districts.

London Water Hardness by Postcode
By county

Counties in London

Sorted by hardness — see how your county compares.

County Hardness PPM Level Postcodes
Greater London
286
286 ppm Hard 330
Suppliers

Water Companies in London

Tap on a company for full coverage area and hardness data.

Affinity Water

268 ppm Hard

SES Water

239 ppm Hard

Severn Trent Water

222 ppm Hard

South East Water

297 ppm Hard

Thames Water

302 ppm Very Hard

Yorkshire Water

215 ppm Hard

Hard Water Guides

Learn more about water hardness and how to manage it.

What Is Water Hardness? Hard Water Effects Solutions
Recommended

Products for London

Top picks for households in hard water areas.

Water2Buy W2B200 Water Softener

From ~£400

Best-value whole-house ion-exchange softener for UK homes. Eliminates limescale from pipes, boilers, and appliances. Digital metered regeneration — low salt use. 7-year warranty.

View on Amazon

Philips AWP1775 Shower Filter

From ~£30

Instant improvement for skin and hair. Reduces chlorine and limescale at the showerhead — no plumbing needed. A good first step before committing to a full softener.

View on Amazon
FAQ

Common questions about London water

Is tap water in London safe to drink?
Yes. All tap water in London meets UK drinking water standards. Hardness affects taste and limescale buildup but not safety.
Why is water in London hard?
Water hardness in London depends on the geology — chalk and limestone aquifers dissolve calcium and magnesium into the supply, making it harder. Areas with sandstone or granite tend to be softer.
Does hard water affect boilers in London?
Over time, limescale acts as an insulator in heat exchangers, reducing efficiency by a few percentage points each year if untreated. A water softener can help protect your boiler.
What's the average water hardness in London?
The average water hardness across London is 286 ppm (parts per million), classified as hard. It ranges from 150 ppm to 350 ppm across 330 postcode districts.

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